The project concerns the upgrade of energy efficiency, energy saving and utilization of Renewable Energy Sources RES at Istiaia Gymnasium The aim is through a dynamic and multifaceted intervention in the shell and systems of the building to reduce the annual operating cost as well as to improve the conditions of thermal comfort inside the premisesTo serve these objectives, interventions are provided that include the application of an external thermal insulation system for walls, the application of thermal insulation of the roof, the replacement of windows and doors, the energy upgrade of the heating and lighting system, the installation of a building energy management system and the installation of photovoltaic systems